1. Field
The invention relates to in situ recovery of shale oil and gas from naturally porous, water-flooded, subterranean oil shale formations.
2. State of the Art
Due to the relative high cost of mining oil shale for subsequent, above-ground processing, efforts are continually being made to recover the kerogen, i.e. the organic content, from the shale in situ. Heretofore, such efforts have been largely directed to thermal decomposition of the kerogen by burning a portion thereof in situ to supply much or all of the decomposing heat required. In other instances, hot fluids have been circulated through the shale after it has been rendered pervious in one way or another.
In some instances, oil shale formations are naturally fractured and pervious. This is true of certain oil shale strata occurring in the Parachute Creek member of the Green River formation in the Piceance Creek Basin of northwestern Colorado. However, these strata are generally flooded with water. The fractured nature of the strata and the water flooding make mining and the usual in situ recovery techniques impractical.